Air pollution fell by only 28 per cent during the most recent lockdowns across the UK compared with a halving during the first lockdown, despite restrictions and ensuing drops in traffic being similar.
The difference is probably explained by increased air pollution from gas boilers as people worked from home and tried to keep warm during the winter, says Rhianna Evans at University of York, UK, who led the study into levels of the toxic gas nitrogen dioxide (NO2).
鈥淐ovid has provided us with a glimpse into the future of air pollution,鈥� says Evans. The UK鈥檚 NO2 pollution from cars and lorries is due to fall in coming years due to electric vehicle take-up, but more remote working and reliance on gas boilers for heating will make the contribution of homes more important.
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Evans and her colleagues examined data from 30 air pollution monitoring sites across the UK to build a representative picture of how NO2 and ozone levels responded to covid-19 restrictions around the country. Traffic levels were gleaned from , which uses anonymised travel data from the phones of Google users. The severity of restrictions were measured by , which compares indicators such as school closures and travel restrictions around the world.
During both the March-May 2020 lockdown across the UK and the period between January and March 2021 鈥� which aligned with lockdown in England, though lockdowns in Scotland, Wales and Northern Ireland lasted longer 鈥� traffic was down about 70 per cent and the restrictions were similarly high. Yet NO2 emissions fell nearly twice as much during the 2020 lockdown as they did during the 2021 lockdown.
鈥淕as boilers kicking more nitrogen dioxide into our air last year is backed up by government data showing that residential carbon emissions were also higher as we all spent more time at home during lockdown,鈥� says Jess Ralston at the Energy and Climate Intelligence Unit in the UK.
Evans says it is likely that gas boilers in homes offset the savings in the winter of 2021 鈥� a due to greater home working.
One side effect of the reduction in NO2 was an average 21 per cent increase in ozone during the first lockdown, because the amount of NO2 in the air plays a role in the formation of ozone. Evans says that makes a case that we should be gathering more data with ozone sensors, because the pollutant isn鈥檛 currently monitored as comprehensively as NO2. Her work was presented at a meeting of the European Geosciences Union on 27 April.
The UK government has consistently been in breach of legal limits for NO2 for more than a decade, and illegal levels of the gas were last year found by an inquest to have played a role in the death of a 9-year old girl in London.
鈥淚t is clear that decisions currently being made on how to stay warm at home without warming the planet can bring advantages beyond saving millions of tonnes of carbon from entering the atmosphere. The health and well-being benefits of cleaner air and healthier homes are well known, and will likely spur ministers on towards ambitious action to clean up domestic heat,鈥� says Ralston.
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